[all][infra] Zuul logs are in swift

Hi,
We have made the switch to begin storing all of the build logs from Zuul
in Swift.
Each build's logs will be stored in one of 7 randomly chosen Swift
regions in Fort Nebula, OVH, Rackspace, and Vexxhost. Thanks to those
providers!
You'll note that the links in Gerrit to the Zuul jobs now go to a page
on the Zuul web app. A lot of the features previously available on the
log server are now available there, plus some new ones.
If you're looking for a link to a docs preview build, you'll find that
on the build page under the "Artifacts" section now.
If you're curious about where your logs ended up, you can see the Swift
hostname under the "logs_url" row in the summary table.
Please let us know if you have any questions or encounter any issues,
either here, or in #openstack-infra on IRC.
-Jim